KR102238769B1 - Composition for forming electrode, electrode manufactured using the same and solar cell - Google Patents

Abstract

상기 화학식 1 및 2의 각 치환기의 정의는 상세한 설명에 기재된 바와 같다.It provides a composition for forming an electrode comprising a conductive powder, a glass frit, an organic binder including a polymer containing a structural unit represented by the following formula (1), a block isocyanate compound represented by the following formula (2), and a solvent.
[Formula 1] [Formula 2]

The definitions of each substituent in Formulas 1 and 2 are as described in the detailed description.

Description

Composition for electrode formation, and electrode and solar cell manufactured therefrom TECHNICAL FIELD {COMPOSITION FOR FORMING ELECTRODE, ELECTRODE MANUFACTURED USING THE SAME AND SOLAR CELL}

It relates to a composition for forming an electrode, an electrode prepared therefrom, and a solar cell.

Solar cells generate electrical energy using the photoelectric effect of a pn junction that converts photons of sunlight into electricity. In a solar cell, a front electrode and a rear electrode are formed on upper and lower surfaces of a semiconductor substrate (semiconductor wafer) on which a pn junction is formed. In the solar cell, the photoelectric effect of the pn junction is induced by sunlight incident on a substrate, and electrons generated therefrom provide a current flowing to the outside through an electrode.

The electrode of such a solar cell may be formed in a predetermined pattern on the surface of the substrate by applying, patterning, and firing the electrode-forming composition.

In order to improve the conversion efficiency of the solar cell, the contact resistance (Rc) and series resistance (Rs) are minimized by improving the contact property with the substrate, or by adjusting the pattern line width of the screen mask to a small size with an organic material. line) to increase the short-circuit current (I _sc ) is known. However, a method of reducing the electrode pattern line width using a screen mask may cause an increase in series resistance Rs, and may deteriorate the continuous printability of a fine pattern.

The composition for forming an electrode uses an organic vehicle to impart viscosity and rheological properties suitable for printing, and the organic vehicle may generally include an organic binder and a solvent.

As a measure to increase dispersibility and storage stability, the content of the organic binder may be increased, or a number of organic binders having a high molecular weight may be used.

When the content of the organic binder is increased, the resistance may increase during electrode formation, and when a high-molecular-weight organic binder is used, the viscosity increases even at a high shear rate, resulting in a tailing phenomenon and poor printing. There is a problem that there is.
[Prior technical literature]
[Patent Document 1] Korean Patent Application Publication No. 10-2012-0069159 (2012.06.28.)
[Patent Document 2] Japanese Laid-Open Patent Publication No. 2012-038625 (2012.02.23.)

One embodiment provides a composition for forming an electrode capable of forming a fine pattern of high resolution, excellent printing characteristics, and excellent dispersibility and storage stability.

Another embodiment provides an electrode made of the electrode-forming composition.

Another embodiment provides a solar cell including the electrode.

According to one embodiment, conductive powder; Glass frit; An organic binder containing a polymer containing a structural unit represented by the following formula (1); Block isocyanate compounds represented by the following formula (2); And it provides a composition for forming an electrode comprising a solvent.

[Formula 1]

In Formula 1,

R ¹ is a substituted or unsubstituted linear or branched C1 to C10 alkyl group,

X is from 50 mol% to 90 mol%,

Y is from 10 mol% to 50 mol%.

[Formula 2]

In Chemical Formula 2,

BL is methylethyl ketoxime, caprolactam, 3,5-dimethyl pyrazole, 1,2,4-triazole , Imidazole, 2-butanine diethyl malonate or ethylacetoacetate,

R ² is a substituted or unsubstituted linear or branched C1 to C10 alkyl group.

The mixing weight ratio of the organic binder including the polymer containing the structural unit represented by Formula 1 and the block isocyanate compound represented by Formula 2 may be 30:1 to 1:1.

The polymer including the structural unit represented by Formula 1 may further include a structural unit represented by Formula 3 below.

[Formula 3]

In Chemical Formula 3,

R ³ is hydrogen or a methyl group,

R ⁴ is a substituted or unsubstituted linear or branched C1 to C10 alkyl group,

Z is from 0.01 mol% to 30 mol%.

The structural unit represented by Formula 3 may be included in an amount of 0.1 mol% to 30 mol% based on 100 mol% of the polymer including the structural unit represented by Formula 1.

The weight average molecular weight (Mw) of the polymer including the structural unit represented by Formula 1 may be 1,000 g/mol to 300,000 g/mol.

The electrode-forming composition includes 60 to 95% by weight of the conductive powder; 0.5 to 20% by weight of the glass frit; 1 to 20% by weight of an organic binder containing a polymer containing the structural unit represented by Formula 1; 0.1 to 5% by weight of the block isocyanate compound represented by Chemical Formula 2; And the remaining amount of the solvent.

The glass frit is lead (Pb), tellurium (Te), bismuth (Bi), lithium (Li), phosphorus (P), germanium (Ge), gallium (Ga), cerium (Ce), iron (Fe), Silicon (Si), zinc (Zn), tungsten (W), magnesium (Mg), cesium (Cs), strontium (Sr), molybdenum (Mo), titanium (Ti), tin (Sn), indium (In), Vanadium (V), barium (Ba), nickel (Ni), copper (Cu), sodium (Na), potassium (K), arsenic (As), cobalt (Co), zirconium (Zr), manganese (Mn) and It may contain at least one metal element selected from aluminum (Al).

The solvent is methyl cellosolve, ethyl cellosolve, butyl cellosolve, aliphatic alcohol, α-terpineol, β-terpineol, Selected from dihydro-terpineol, ethylene glycol, ethylene glycol monobutyl ether, butyl cellosolve acetate and Texanol. It may include at least one.

The electrode-forming composition may further include one or more additives selected from a surface treatment agent, a dispersant, a thixotropic agent, a viscosity stabilizer, a plasticizer, a defoaming agent, a pigment, an ultraviolet stabilizer, an antioxidant, and a coupling agent.

Another embodiment provides an electrode made of the electrode-forming composition.

Another embodiment provides a solar cell including the electrode.

The electrode-forming composition is capable of forming a fine pattern of high resolution, has excellent printing properties, and has excellent dispersibility and storage stability.

1 is a schematic diagram schematically showing the structure of a solar cell according to an embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

In the drawings, the thicknesses are enlarged in order to clearly express various layers and regions. Like reference numerals are attached to similar parts throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case where the other part is "directly above", but also the case where there is another part in the middle. Conversely, when one part is "directly above" another part, it means that there is no other part in the middle.

Unless otherwise specified herein, "substituted" means that at least one hydrogen atom is halogen (F, Cl, Br or I), hydroxy group, C1 to C20 alkoxy group, nitro group, cyano group, amino group, imino group, azi Pottery, amidino group, hydrazino group, hydrazono group, carbonyl group, carbamyl group, thiol group, ester group, ether group, carboxyl group or salt thereof, sulfonic acid group or salt thereof, phosphoric acid group or salt thereof, C1 to C20 alkyl group, C2 to C20 alkenyl group, C2 to C20 alkynyl group, C6 to C30 aryl group, C3 to C20 cycloalkyl group, C3 to C20 cycloalkenyl group, C3 to C20 cycloalkynyl group, C2 to It means substituted with a substituent selected from a C20 heterocycloalkyl group, a C2 to C20 heterocycloalkenyl group, a C2 to C20 heterocycloalkynyl group, a C3 to C30 heteroaryl group, or a combination thereof.

In addition, unless otherwise specified in the specification, "hetero" means that at least one hetero atom of at least one of N, O, S and P is included in the cyclic group.

The composition for forming an electrode according to an embodiment may include a conductive powder; Glass frit; Organic binders; And a solvent.

Hereinafter, the present invention will be described in detail.

The electrode-forming composition may use a metal powder as a conductive powder. The metal powder is silver (Ag), gold (Au), palladium (Pd), platinum (Pt), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir), rhenium (Re), and titanium. (Ti), niobium (Nb), tantalum (Ta), aluminum (Al), copper (Cu), nickel (Ni), molybdenum (Mo), vanadium (V), zinc (Zn), magnesium (Mg), yttrium It may include one or more metals selected from (Y), cobalt (Co), zirconium (Zr), iron (Fe), tungsten (W), tin (Sn), chromium (Cr) and manganese (Mn), It is not limited to this.

The conductive powder may be a powder having a nano-sized or micro-sized particle diameter, for example, a conductive powder having a size of tens to hundreds of nanometers, a conductive powder having a size of several to tens of micrometers, and having two or more different sizes. It is also possible to mix and use conductive powder.

The conductive powder may have a spherical shape, a plate shape, or an amorphous shape. The average particle diameter (D50) of the conductive powder is preferably 0.1 μm to 10 μm, more preferably 0.5 μm to 5 μm. The average particle diameter was measured using a 1064LD model manufactured by CILAS after dispersing the conductive powder in isopropyl alcohol (IPA) by ultrasonic waves at room temperature (20 to 25°C) for 3 minutes. Within the above range, contact resistance and line resistance may be lowered.

The conductive powder may be included in an amount of 60 to 95% by weight based on 100% by weight of the total amount of the composition for forming an electrode. In the above range, it is possible to prevent the conversion efficiency from being lowered due to an increase in resistance, and it is possible to prevent it from becoming difficult to form a paste due to a relative decrease in the amount of the organic vehicle. Preferably it may be included in 70 to 90% by weight.

The glass frit generates metal crystal particles of conductive powder in the emitter region so that resistance is lowered by etching the antireflection film during the firing process of the electrode forming composition and melting the conductive powder particles, It improves the adhesion between the conductive powder and the wafer and softens during sintering to induce the effect of lowering the sintering temperature.

In order to increase the efficiency of the solar cell, if the area of the solar cell is increased, the contact resistance of the solar cell may increase. Therefore, it is necessary to minimize the damage to the pn junction and at the same time minimize the series resistance. In addition, as the number of substrates having various sheet resistances increases, the sintering temperature increases, so it is preferable to use a glass frit capable of sufficiently securing thermal stability even at a wide sintering temperature.

The glass frit may be any one or more of a flexible glass frit and a lead-free glass frit commonly used in a composition for forming an electrode.

The glass frit is lead (Pb), tellurium (Te), bismuth (Bi), lithium (Li), phosphorus (P), germanium (Ge), gallium (Ga), cerium (Ce), iron (Fe), Silicon (Si), zinc (Zn), tungsten (W), magnesium (Mg), cesium (Cs), strontium (Sr), molybdenum (Mo), titanium (Ti), tin (Sn), indium (In), Vanadium (V), barium (Ba), nickel (Ni), copper (Cu), sodium (Na), potassium (K), arsenic (As), cobalt (Co), zirconium (Zr), manganese (Mn) and It may contain at least one metal element selected from aluminum (Al).

The glass frit may be derived from an oxide of the metal element described above using a conventional method. For example, it can be obtained by melting a mixture prepared by mixing oxides of metal elements in a specific composition, quenching, and then grinding again. The mixing process may be performed using a ball mill or a planetary mill. The melting process may be performed under conditions of 700°C to 1300°C, and the quenching process may be performed at room temperature (20 to 25°C). The pulverization process may be performed by a disk mill, a planetary mill, or the like, but is not limited thereto.

The glass frit may have an average particle diameter (D50) of 0.1 μm to 10 μm, and may be included in an amount of 0.5 to 20% by weight based on 100% by weight of the total amount of the composition for forming an electrode. Within the above range, it is possible to improve the adhesion strength of the electrode in a range that does not impair the electrical properties of the electrode.

The shape of the glass frit may be spherical or non-shape. In one embodiment, two types of glass frit having different transition temperatures may be used. For example, a first glass frit having a transition temperature of 200° C. or more and 350° C. or less and a second glass frit having a transition temperature of more than 350° C. and 550° C. or less may be mixed and used in a weight ratio of 1:0.2 to 1:1.

The composition for forming an electrode may include a polymer including a structural unit represented by Formula 1 below as an organic binder.

[Formula 1]

In Formula 1,

R ¹ is a substituted or unsubstituted linear or branched C1 to C10 alkyl group,

X is from 50 mol% to 90 mol%,

Y is from 10 mol% to 50 mol%.

The polymer containing the structural unit represented by Formula 1 has a polyvinyl acetal structure and a polyvinyl alcohol structure. Polyvinyl acetal is usually produced from a vinyl alcohol-based polymer as a raw material. The polyvinyl alcohol can be obtained by a conventionally known method, that is, by polymerizing a vinyl ester-based monomer and saponifying the obtained polymer. As a method of polymerizing the vinyl ester-based monomer, a conventionally known method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, and an emulsion polymerization method can be applied. As the polymerization initiator, an azo initiator, a peroxide initiator, a redox initiator, and the like are appropriately selected depending on the polymerization method. As for the saponification reaction, alcohol decomposition and hydrolysis using a conventionally known alkali catalyst or an acid catalyst can be applied, and among them, the saponification reaction using methanol as a solvent and a caustic soda (NaOH) catalyst is simple and most preferred. .

The average polymerization degree of polyvinyl alcohol used as the raw material of the polyvinyl acetal used in the present invention is appropriately selected depending on the application, but it is preferably 150 to 3,000, and more preferably 200 to 2,000.

The acid catalyst used in the acetalization reaction is not particularly limited, and any of an organic acid and an inorganic acid can be used, and examples thereof include acetic acid, paratoluenesulfonic acid, nitric acid, sulfuric acid, hydrochloric acid, and the like. Among these, hydrochloric acid, sulfuric acid, and nitric acid are preferably used, and hydrochloric acid is particularly preferably used.

The aldehyde used in the acetalization reaction of the present invention is not particularly limited, but it is preferable to use polyvinyl acetal acetalized with an aldehyde having 1 to 8 carbon atoms. As aldehydes having 1 to 8 carbon atoms, formaldehyde, acetaldehyde, propionaldehyde, n-butylaldehyde, isobutylaldehyde, n-hexylaldehyde, 2-ethylbutylaldehyde, n-octylaldehyde, 2-ethylhexylaldehyde, benzaldehyde, etc. These may be mentioned, and these may be used individually, and 2 or more types may be used together. Among these, aldehydes having 4 to 6 carbon atoms, particularly n-butylaldehyde are preferably used.

That is, as polyvinyl acetal, polyvinyl butyral is particularly preferable.

The average degree of acetalization of the polyvinyl acetal is preferably 40 to 85 mol%, preferably 48 to 82 mol%, and more preferably 55 to 81 mol%. In addition, in order to achieve the object of the present invention more suitably, the content of the vinyl ester unit of the polyvinyl acetal (usually, the content of the vinyl acetate unit) is 0.01 to 30 mol%, preferably 0.05 to 15 mol%, more suitably. Is preferably 0.1 to 5 mol%. Further, the vinyl alcohol unit content is 10 to 50 mol%, preferably 12 to 40 mol%, and optimally 15 to 35 mol%. In addition, the values of the acetalization degree, the vinyl ester unit content, and the vinyl alcohol unit content are values with respect to the total amount of the acetalization degree (vinyl acetal unit content), the vinyl ester unit content, and the vinyl alcohol unit content.

In addition, the polymer including the structural unit represented by Formula 1 may further include a structural unit represented by Formula 3:

[Formula 3]

In Chemical Formula 3,

R ³ is hydrogen or a methyl group,

R ⁴ is a substituted or unsubstituted linear or branched C1 to C10 alkyl group,

Z is from 0.01 mol% to 30 mol%.

The structural unit represented by Formula 3 may be included in an amount of 0.1 mol% to 30 mol% based on 100 mol% of the polymer including the structural unit represented by Formula 1. When the structural unit of Formula 3 is included in the above range, dispersibility and printing characteristics of the composition for forming an electrode may be improved.

The weight average molecular weight (Mw) of the polymer including the structural unit represented by Formula 1 may be 1,000 g/mol to 300,000 g/mol. In the above range, it is possible to improve the dispersibility and printing properties of the electrode-forming composition.

In addition, the composition for forming an electrode may include a block isocyanate compound represented by Formula 2 below.

[Formula 2]

In Chemical Formula 2,

BL is methylethyl ketoxime, caprolactam, 3,5-dimethyl pyrazole, 1,2,4-triazole , Imidazole, 2-butanine diethyl malonate or ethylacetoacetate,

R ² is a substituted or unsubstituted linear or branched C1 to C10 alkyl group.

In particular, the block isocyanate compound represented by Formula 2 has excellent stability at room temperature, and crosslinking of the organic binder and isocyanate at the silver paste drying temperature (250 to 400°C) while the blocking agent of the block isocyanate is dissociated (dissociation temperature: 100 to 200°C). It controls the line width bleeding phenomenon by the reaction reaction, and is effective in improving the adhesion to the silicon wafer as the substrate by urethane bonding.

The mixing weight ratio of the organic binder containing the polymer containing the structural unit represented by Chemical Formula 1 and the fluoroisocyanate compound represented by Chemical Formula 2 is 30:1 to 1:1, specifically 10:1 to 1:1 days I can. In the above range, it is more effective in controlling line width spreading and improving adhesion to the silicon wafer.

In addition to the above-described block isocyanate compound, the electrode-forming composition may further include conventional additives as necessary in order to improve flow characteristics, process characteristics, and stability. The additive may be used alone or in combination of two or more of a surface treatment agent, a dispersant, a thixotropic agent, a viscosity stabilizer, a plasticizer, an antifoaming agent, a pigment, an ultraviolet stabilizer, an antioxidant, a coupling agent, and the like.

These may be included in an amount of 0.1 to 5% by weight based on 100% by weight of the total amount of the composition for forming an electrode, but the content may be changed as necessary. The content of the additive may be selected in consideration of printing characteristics, dispersibility, and storage stability of the composition for forming an electrode.

The electrode-forming composition is 60 to 95% by weight of conductive powder; 0.5 to 20% by weight of glass frit; 1 to 20% by weight of an organic binder containing a polymer containing the structural unit represented by Formula 1; 0.1 to 5% by weight of the block isocyanate compound represented by Chemical Formula 2; And the residual amount of the solvent. In the above range, an appropriate viscosity of the composition for forming an electrode can be obtained, so that the adhesion to the substrate can be prevented from deteriorating, and the organic binder is not decomposed smoothly during firing, resulting in high resistance, and cracking, opening, and pinhole of the electrode during the firing process. It can prevent problems such as.

The solvent has a boiling point of 100°C or higher, and includes methyl cellosolve, ethyl cellosolve, butylcellosolve, aliphatic alcohol, and α-terpineol. ), β-terpineol, dihydro-terpineol, ethylene glycol, ethylene glycol mono butyl ether, butyl cellosolve acetate, Texanol, etc. may be used alone or in combination of two or more.

The solvent may be included in the balance of the composition for forming an electrode, and specifically, may be included in an amount of 1 to 30% by weight based on 100% by weight of the total amount of the composition for forming an electrode. Sufficient adhesive strength and excellent printability can be secured within the above range.

According to another embodiment, an electrode formed from the electrode-forming composition is provided.

According to another embodiment, a solar cell including the electrode is provided.

A solar cell according to an embodiment will be described with reference to FIG. 1. 1 is a schematic diagram schematically showing the structure of a solar cell according to an embodiment.

Referring to FIG. 1, on a substrate 100 including a p-layer (or n-layer) 101 and an n-layer (or p-layer) 102 as an emitter, a composition for forming an electrode is printed and fired to The electrode 210 and the front electrode 230 may be formed. For example, after printing the composition for forming an electrode on the rear surface of the substrate, drying it at a temperature of about 200° C. to 400° C. for about 10 to 60 seconds to perform a preliminary preparation step for the rear electrode. A paste made by mixing an organic binder containing a polymer containing a structural unit represented by Chemical Formula 1 and a block isocyanate represented by Chemical Formula 2 contained in the composition for forming an electrode has excellent storage at room temperature, so viscosity change at room temperature, etc. It does not occur, and the isocyanate generated by dissociation of the block isocyanate in the region of approximately 200°C to 400°C applied by printing may react with the hydroxy group of Formula 1 to form a crosslinked structure.

In addition, the electrode-forming composition may be printed on the entire surface of the substrate and dried to perform a preliminary preparation step for the front electrode. Thereafter, a firing process may be performed at 400° C. to 980° C., preferably 700° C. to 980° C. for about 30 to 210 seconds to form the front electrode and the rear electrode.

Hereinafter, the present invention will be described in more detail through examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention.

Polymer synthesis

< Synthesis example 1>

Add 6.5 g of a 5 wt% aqueous hydrochloric acid solution to 100 g of a 10 wt% polyvinyl alcohol (polymerization degree: 1,700, OCI) aqueous solution to a round bottom flask equipped with a nitrogen atmosphere condenser, and then stir the aqueous solution (temperature is 50 ℃ Retaining) 1.5 g of butyl aldehyde (Across Chemical Co., Ltd., purity 99%) was added and reacted. After cooling to 30° C. or lower, 4.0 g of butyl aldehyde was added. Thereafter, the mixture was heated up to 50° C. again, maintained for 4 hours, and the reaction was terminated. In order to remove unreacted substances from the obtained polymer, it was washed with distilled water and then dried at low temperature to obtain a polyvinyl butyral copolymer having a weight average molecular weight of 130,000 g/mol.

< Synthesis example 2>

A polyvinyl butyral copolymer having a weight average molecular weight of 200,000 g/mol was obtained in the same manner as in Synthesis Example 1, except that polyvinyl alcohol (OCI) having a polymerization degree of 5,000 was used.

Block isocyanate Compound synthesis

< Synthesis example 3>

Hexamethylene diisocyanate trimer (1eq) was added to a round bottom flask equipped with a nitrogen atmosphere condenser, and methylethyl ketoxime (1.5eq) was added as a blocking agent at 75°C to react. after. After confirming that the isocyanate group disappeared (2270cm ^-1 ) by FT-IR, and after the reaction was terminated, butylcellosolve acetate was added to adjust the viscosity to 40,000 cps/25°C, and the structural unit of Formula 2 A blocked isocyanate compound having was obtained.

Preparation of composition for electrode formation

< Example 1>

As an organic binder, 1.5% by weight of the copolymer prepared from Synthesis Example 1 and 1.5% by weight of the copolymer prepared from Synthesis Example 2 were sufficiently dissolved in 6.5% by weight of butyl cellosolve acetate as a solvent at 50°C. Next, 1 wt% of the block isocyanate compound prepared from Synthesis Example 3, a low melting point flexible glass frit having an average particle diameter of 1.0 μm and a transition temperature of 341° C. (Flexible Glass, Paticloji, CI-124) 2.0 wt%, As additives, 0.2% by weight of dispersant BYK102 (BYK-chemie) and 0.3% by weight of thixotropic agent Thixatrol ST (Elementis Co.), spherical silver powder with an average particle diameter (D50) of 1.5㎛ (Dowa, AG-4-8) 87 A composition for forming an electrode was prepared by adding wt% and mixing uniformly, followed by mixing and dispersing with a 3-roll kneader.

< Example 2>

A composition for forming an electrode was prepared in the same manner as in Example 1, except that 2% by weight of the copolymer prepared from Synthesis Example 1 and 1% by weight of the copolymer prepared from Synthesis Example 2 were used as organic binders.

< Example 3>

A composition for forming an electrode was prepared in the same manner as in Example 1, except that 1% by weight of the copolymer prepared from Synthesis Example 1 and 2% by weight of the copolymer prepared from Synthesis Example 2 were used as organic binders.

< Comparative example 1>

Example 1 and Example 1 except that the copolymer prepared from Synthesis Example 1 and the copolymer prepared from Synthesis Example 2 were not used, and 3% by weight of a cellulose binder (Dow Chemical Co., STD 45) polymer was used as an organic binder. A composition for forming a solar cell electrode was prepared in the same manner.

< Comparative example 2>

The copolymer prepared from Synthesis Example 1, the copolymer prepared from Synthesis Example 2, and the block isocyanate compound were not used, and 3% by weight of a cellulose binder (STD 4, manufactured by Dow Chemical) was used as an organic binder, and the solvent was 7.5. A composition for forming a solar cell electrode was prepared in the same manner as in Example 1, except that weight% was used.

< Comparative example 3>

A composition for forming a solar cell electrode was prepared in the same manner as in Example 1, except that a block isocyanate compound was not used and 7.5% by weight of a solvent was used.

Method of property evaluation

(1) Storage stability ( % )

Storage stability was evaluated by the viscosity change rate before and after storage of the electrode-forming composition prepared according to Equation 1 below, and the results are shown in Table 1 below.

[Equation 1]

(F ₀ : Viscosity value measured at room temperature (25°C) after storing the electrode-forming composition at 25°C and 50±5% relative humidity for 1 day

F ₁ : After storing the electrode-forming composition for 30 days at 25°C and 50±5% relative humidity, the viscosity value measured at room temperature (25°C))

※ Viscosity measurement: Using a Brookfield viscometer (HBDV-2+pro), an SC4-14 spindle and an SC4-6RP chamber were mounted, preshear was applied at 25℃ at 10 rpm for 30 seconds, and the value was measured.

(2) fine pattern evaluation

The electrode-forming compositions according to Examples 1 to 3 and Comparative Examples 1 to 3 were screen-printed on the entire surface of a poly P-type silicon wafer having a surface resistance of 90Ω using a screen mask, respectively, to print a finger bar. And dried using an infrared drying furnace. Thereafter, a composition for forming an electrode including aluminum was printed on the back side of the wafer and dried in the same manner. The cell formed by the above process was fired for 30 to 50 seconds between 400 and 950 °C using a belt-type kiln, and an EL tester (MV Tech Co., Ltd.) was used to check whether the manufactured electrode (finger bar) was disconnected. The number of line openings was measured, and the line width and thickness of the electrode line were measured using a VK equipment (KEYENCE Corporation VK9710), and the results are shown in Table 1 below.

* Screen mask: SUS325 type / Emulsion thickness 15㎛ / Finger bar line width 45㎛, Number of finger bars 80

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Storage stability (%) 5 5 5 5 4 4 Line width after printing L1 (㎛) 61 60 58 59 60 63 Line width after drying L2 (㎛) 63 62 60 61 66 71 Line width after firing L3 (㎛) 64 62 60 63 68 73 Thickness D1 after firing (㎛) 21 22 21 20 20 19 Line width△ (L1-L2) (㎛) △2 △2 △2 △2 △6 △8 Aspect Ratio (D1/L3) 0.328 0.355 0.350 0.317 0.294 0.260

Referring to Table 1, it is understood that the composition for forming an electrode according to Examples 1 to 3 has excellent storage stability compared to the composition for forming an electrode according to Comparative Examples 1 to 3, and the line width of the electrode pattern prepared therefrom is also fine Able to know.

Simple modifications or changes of the present invention can be easily implemented by those of ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

100: substrate 101: p-layer (or n-layer)
102: n-layer (or p-layer) 210: rear electrode
230: front electrode

Claims (11)

Conductive powder;
Glass frit;
An organic binder containing a polymer containing a structural unit represented by the following formula (1);
Block isocyanate compounds represented by the following formula (2); And
menstruum
Including,
The mixing weight ratio of the organic binder containing the polymer containing the structural unit represented by Formula 1 and the block isocyanate compound represented by Formula 2 is 30:1 to 1:1,
The polymer containing the structural unit represented by Formula 1 is a composition for forming an electrode further comprising a structural unit represented by the following Formula 3:
[Formula 1]

In Formula 1,
R ¹ is a substituted or unsubstituted linear or branched C1 to C10 alkyl group,
X is from 50 mol% to 90 mol%,
Y is from 10 mol% to 50 mol%;
[Formula 2]

In Chemical Formula 2,
BL is methylethyl ketoxime, caprolactam, 3,5-dimethyl pyrazole, 1,2,4-triazole , Imidazole, 2-butanine diethyl malonate or ethylacetoacetate,
R ² is a substituted or unsubstituted linear or branched C1 to C10 alkyl group,
[Formula 3]

In Chemical Formula 3,
R ³ is hydrogen or a methyl group,
R ⁴ is a substituted or unsubstituted linear or branched C1 to C10 alkyl group,
Z is from 0.01 mol% to 30 mol%. delete delete delete The method of claim 1,
A composition for forming an electrode having a weight average molecular weight (Mw) of 1,000 g/mol to 300,000 g/mol of the polymer containing the structural unit represented by Formula 1 above. The method of claim 1,
60 to 95% by weight of the conductive powder;
0.5 to 20% by weight of the glass frit;
1 to 20% by weight of an organic binder containing a polymer containing the structural unit represented by Formula 1;
0.1 to 5% by weight of the block isocyanate compound represented by Chemical Formula 2; And
The residual amount of the solvent
Composition for forming an electrode comprising a. The method of claim 1,
The glass frit is lead (Pb), tellurium (Te), bismuth (Bi), lithium (Li), phosphorus (P), germanium (Ge), gallium (Ga), cerium (Ce), iron (Fe), Silicon (Si), zinc (Zn), tungsten (W), magnesium (Mg), cesium (Cs), strontium (Sr), molybdenum (Mo), titanium (Ti), tin (Sn), indium (In), Vanadium (V), barium (Ba), nickel (Ni), copper (Cu), sodium (Na), potassium (K), arsenic (As), cobalt (Co), zirconium (Zr), manganese (Mn) and A composition for forming an electrode comprising at least one metal element selected from aluminum (Al). The method of claim 1,
The solvent is methyl cellosolve, ethyl cellosolve, butyl cellosolve, aliphatic alcohol, α-terpineol, β-terpineol, Selected from dihydro-terpineol, ethylene glycol, ethylene glycol monobutyl ether, butyl cellosolve acetate and Texanol. A composition for forming an electrode comprising at least one. The method of claim 1,
The composition for forming an electrode further comprises at least one additive selected from a surface treatment agent, a dispersant, a thixotropic agent, a viscosity stabilizer, a plasticizer, a defoaming agent, a pigment, a UV stabilizer, an antioxidant and a coupling agent. An electrode made of the composition for forming an electrode of any one of claims 1 and 5 to 9. A solar cell comprising the electrode according to claim 10.

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